A rotating bed known from DE 199 12 937 has a height-adjustable base. The base stands freely in a conventional bed frame. A rotary joint arranged on the base serves to connect the base to a bed or mattress frame. The bed or mattress frame is frequently divided into four sections, viewed in the longitudinal direction of the bed, namely a back part or back section, a central section, a thigh section, and a lower leg section.
The central section is directly connected to the base by means of the rotary joint, the axis of which extends vertically. The back section is coupled to the central section by means of a hinge arrangement with a horizontal axis, and a thigh section is similarly connected to the central section on the opposite end. The lower leg section is coupled to the free end of the thigh section by means of a hinge arrangement with a horizontal axis.
In order to enhance stability, the base has relatively large dimensions in the longitudinal direction of the bed. However, it cannot project beyond the structure of the bed frame in the lateral direction.
In the normal bed or sleeping position, the bed frame is essentially flat and its longitudinal axis extends parallel to the longitudinal axis of the floor coverage area defined by the contact points between the base and the floor.
In order to transfer a person lying in the bed into a sitting position, the back section is initially raised into an approximately 80° position with the aid of a motor. The thigh section and the lower leg section also are moved into a slightly raised position in order to provide the user with a sense of stability during the subsequent rotation.
After the bed frame is moved into this position, it is turned on the base by approximately 90° until the thigh section and the lower leg section transversely extend over the side of the bed. The term side of the bed refers to the conventional definition or meaning.
As soon as the bed frame is transversely aligned in this fashion, the thigh section and the lower leg section are lowered, wherein the lower leg section is lowered to such a degree that it essentially extends vertically. The bed frame now has a chair-like configuration, in which the free end of the lower leg section is practically in contact with the floor.
At this time, the front edge of the seat projects significantly beyond the side of the floor coverage area of the base. This arrangement may approach its stability limit, particularly when the bed frame is raised, depending on the weight of the user, the distance by which the user leans forward over the seat edge in the chair position, the weight of the base, the size of the floor coverage area of the base and any impermissible manipulations the patient during the rotation. If the stability limit is exceeded, the bed could completely tip over on the side concerned, and the user can be trapped underneath the bed.